The present invention relates generally to printing on continuously moving sheet-type work materials using inkjet, dot matrix, thermal, or like print heads, and deals more particularly with a method for increasing the throughput of a printing apparatus wherein the web moves continuously.
Printing apparatuses that print on a continuously moving web are well known in the art. Examples include the printing apparatuses disclosed in U.S. Pat. No. 6,076,983 entitled xe2x80x9cMethod and Apparatus for Printing onto a Continuously Advancing Web of Work Materialxe2x80x9d and U.S. Pat. No. 6,056,454 entitled xe2x80x9cMethod and Apparatus-for Printing on a Continuously Moving Sheet of Work Material,xe2x80x9d both of which are assigned to Gerber Technology, Inc., the assignee of this application. Both patents are incorporated in their entirety herein by reference.
These patents are each directed to apparatuses and methods for printing on a continuously moving sheet of work material (hereinafter a web) that includes a frame defining a work supporting surface and a web that continuously advances through the apparatus in an X coordinate direction longitudinal of itself, and a print head positioned above the work supporting surface such that the web can pass between the print head and the work supporting surface. The print head is positioned adjacent the work supporting surface continuously moves the print head across the work supporting surface such that printing can occur in both an X coordinate direction and a Y coordinate direction approximately perpendicular to the X direction, thereby permitting lineal lines of print positioned proximate to and abutting one another to be printed on the continuously moving web. This would for example allow a continuous graphic to be printed without stopping the forward continuous advancement of the web.
A difficulty associated with printers of this type is that the web throughput is constrained by print head printing speeds. In an effort to address this problem, efforts have been made to increase the rate at which the print head transferred ink or other print media to the web. However, a problem still exists in that the speed at which the web is advanced remains unacceptably slow.
It would be beneficial if printing rates could be varied in those areas where the print head is not required to transfer ink, or other print media, to the web, hereinafter referred to as white space. For example, when a plurality of pattern pieces are arranged upon a marker for printing, white space (non-printer-dictated, unprinted areas between pieces) is inevitable. White space may also occur within a piece. White space can be lineal (within the print line) or longitudinal (across at least one print line). Accordingly, a need exists for a printer whereby the print speed can be increased in the areas of white space. Based on the foregoing, it is the general object of the present invention to provide a printer and method for controlling the printer that overcomes the problem and drawbacks of prior art printers.
The present invention is directed in one aspect to a method for varying the rate of advancement of a continuously advancing web through a printer. To practice this method, a printer is provided having means for continuously advancing a web of sheet-type work material therethrough in a first coordinate direction longitudinal of itself. The printer also includes a print head movable, in response to commands signals generated by a controller, in the first coordinate direction, and also in a second coordinate direction approximately perpendicular to the first coordinate direction. The controller is in communication with the printer and sends command signals thereto to operate the printer during the performance of a printing operation. Data corresponding to a desired printed graphic is stored in the controller in a format, e.g. machine language, understandable by the printer.
The printer also includes a print head coupled thereto and movable in the first coordinate direction as well as a second coordinate direction approximately perpendicular to the first. The co-action of the continuously advancing web, and the motion of the print head, allow lineal lines of print media to be transferred onto the web by the print head along a path approximately perpendicular to the first coordinate direction in response to command signals generated by the controller. Depending on the desired graphic to be printed, the lineal lines of print media can abut one another so that a continuous image is generated.
The controller is programmed to evaluate the graphic data stored therein to detect non-printed areas or white space. During a printing operation the continuous advancement of the web, as well as movement of the print head can be adjusted so that the rate of movement of the print head, the rate of advancement of the web, or both are varied to accelerate through the white space. This has the advantage of decreasing the time required to complete a printing operation. Where multiple graphics are to be printed in a single printing operation, the controller is also programmed to account for areas of white space between graphics and accelerates the print head and/or the advancement of the web accordingly.
Preferably, the printer employed in the method of the present invention includes a frame and means for continuously advancing the web in the first coordinate direction longitudinally of itself at a velocity "ugr"wx relative to the frame. At least one print head is coupled to the frame for movement relative thereto; the print head includes a plurality of print elements arranged in a scanning array extending in the first coordinate direction. Means are provided for repetitively moving the scanning array of print elements relative to the frame along a path including at least one scan segment and one repositioning segment at such a velocity "ugr"a related to the web velocity "ugr"wx that as the scanning array traverses the scan segment of the path the scanning array has a first velocity component "ugr"ax in the first coordinate direction, and a second velocity component "ugr"ay in a second coordinate direction approximately perpendicular to the first coordinate direction.
The means for repetitively moving the scanning array of print elements further is such that the first velocity component "ugr"ax is equal to "ugr"wx so that the scanning array in traversing the scan segment of the path scans a swath on the web parallel to the first coordinate direction. The scanned swath has a swath height hs. Moreover, the means for repetitively moving the scanning array of print elements moves such that in the time required for moving the scanning array along the full extent of the scan segment of the path the web advances a distance hw in the first coordinate direction that is less than the swath height hs.
Upon traversing the scan segment the scanning array travels along the repositioning segment such that prior or equal to a time taken for the web to advance a distance d, where d=hsxe2x88x92hw the print head is repositioned for immediate movement along a scan segment thereby causing successive swaths of the web scanned by the scanning array to be positioned on the continuously advancing web immediately adjacent to one another. When white space is encountered, the controller generates command signals receivable by the printer that cause a respective one, or all of the velocity components "ugr"w, "ugr"ax, "ugr"ay to accelerate over the white space.
The scanning array can also follow a figure-8 shaped path relative to the frame. To accomplish this the scanning array must travel along a first scan segment having first and second ends, and a second scan segment having third and forth ends, each extending transversely across said web. In addition the first scan segment is oriented at a first angle relative to the X coordinate direction, and the second scan segment is oriented at a second angle approximately equal and opposite to the first angle. Preferably, the second scan segment has a third and forth end adjacent to the second and first ends respectively, of the first scan segment.
In this embodiment a first repositioning segment extends between the and fourth ends of the first and second scan segments respectively. A second repositioning segment also extends between the second and third ends of the first and second scan segments respectively. During operation, the scanning array traverses the first scan segment of the path from the first to the second end at a velocity having a first velocity component "ugr"1ay in the X coordinate direction, and a second velocity component "ugr"1ay in the Y coordinate direction. In this manner, the scanning array scans a first swath on the web parallel to the Y coordinate direction having a first swath height h1s.
As the scanning array traverses the first scan segment, the second velocity component "ugr"1ay is such that in the time required for the array to traverse the full extent of the first scan segment, the web advances a distance hw in the X coordinate direction that is less than the first swath height h1s. Upon traversing the full extent of the first scan segment the scanning array travels along the first repositioning segment in a time less than or equal to the time taken for the web to advance a distance d1, where d1=h1sxe2x88x92h1w. The print head is now repositioned for immediate movement along the second scan segment.
The scanning array next traverses the second scan segment at a velocity "ugr"2a wherein the first velocity component is "ugr"2ax, and the second velocity component is xe2x88x92"ugr"2ay that has a magnitude equal to, and a direction opposite to the second velocity component xe2x88x92"ugr"2ay. In traversing the second scan segment, the scanning array scans a second swath on the web parallel to said Y coordinate direction, having a second swath height h2s. The velocity component xe2x88x92"ugr"2ay is such that in the time required for the scanning array to traverse the full extent of the second scan segment the web advances the distance h2w in said X coordinate direction which is less than the second swath height h2s.
Accordingly, upon traversing the full extent of the second scan segment the scanning array travels along the second repositioning segment in a time less than or equal to the time taken for the web to advance a distance d2, where d2=h2sxe2x88x92h2w. In this manner the print head is repositioned for immediate movement along first scan segment, such that the path traveled by the scanning array is figure-8-shaped relative to the frame. As described above, the controller will cause the printer to accelerate the advancement of the web, or the movement of print head, or both to accelerate past white space.
An advantage of the present invention is that the printer not only continuously advances the web thereby lowering printing times over those of more conventional printers, but further lowers print times by accelerating the advancement of the web, or the movement of the print head, or both over non-print areas or white space.